This invention relates to a process for preparing a multilayered belt comprising at least a polymer layer and a conductive layer by electrodeposition of the layers on a mandrel.
Polymer coatings of thicknesses which are less than about 51 micrometers (2 mils) are typically used in the metal finishing industry to protect metals from corroding and to give them a decorative appearance. Coatings of thicknesses greater than about 51 micrometers are more difficult to obtain and have application in special areas such as insulating coatings in electrical applications such as dielectric receivers and also for free standing films, such as seamless belts. These thick coatings are more difficult to obtain by conventional processes such as spray or dip coating. These conventional processes require repeated applications of thin coatings to obtain thick films. Other limitations of the spray coating process are high equipment cost for air handling, spray equipment and solvent recovery. Also, this process requires extensive factory space for equipment and processing. For polymer film belts, elaborate handling procedures and machinery are also needed for removing a belt after it is formed. Thus, fabrication techniques such as spray and dip coating systems encounter sagging, multiple application steps, long curing times, sizable equipment space requirements, high cost and other associated problems.
Most belts normally have a thickness greater than about 254 micrometers (10 mils) and are usually formed by molding or lamination. Molding is carried out in complex and expensive molds. Molded articles contain flashings that require removal to achieve a smooth outer surface. Laminated belts are usually prepared by applying alternate layers of thermoplastic sheets and reinforcing fabrics. These materials are relatively thick and stiff, and are not suitable for extended cycling over small diameter pulleys or rolls. Other types of belts have been prepared by welding opposite ends of sheets together to form belts having an undesirable seam.
Originally, photoreceptors for electrophotographic imaging systems comprised selenium alloys vacuum deposited on rigid aluminum substrates. Photoreceptors have also been prepared by coating rigid substrates with photoconductive particles dispersed in an organic film forming binder. Coating of rigid drum substrates has been effected by various techniques such as spraying, dip coating, vacuum evaporation, and the like. Rigid drum photoreceptors limit copier and printer design flexibility, are less desirable for flash exposure and are expensive.
Flexible organic photoreceptors in the form of belts have recently become popular. These flexible photoreceptors are manufactured by coating a web and thereafter shearing the web into segments which are then formed into belts by welding opposite ends of the sheared web. The resulting welded seam on the photoreceptor disrupts the continuity of the outer surface of the photoreceptor and must be indexed so that it does not print out during an imaging cycle. In other words, efficient stream feeding of paper and throughput are adversely affected because of the necessity to detect a seam within the length of each sheet of paper. Seam detection is a particularly vexing problem for smaller copier and printer designs. The mechanical and optical devices required for indexing add to the complexity and cost of copiers, duplicators and printers, and reduce the flexibility of design. Welded belts are also less desirable for electrophotographic imaging systems because the seam forms a weak point in the belt and collects toner debris during cleaning, particularly with wiper blade cleaning devices. The seam and wiper blade interaction also causes a disruption in motion quality which impacts registration and timing in applications where multiple images are formed on a single belt.
Flexible seamless photoreceptor substrates enable many cost effective machine designs. Currently, flexible seamless substrates are produced by nickel electrodeposition. However, nickel belts have several disadvantages which include cost and difficulty in handling. Nickel belts are costly because the metal is expensive and thicknesses of &gt;2 mils (50 micrometers) are required to achieve desired mechanical properties. Polymeric belts are potentially cheaper than Ni, are more flexible and are easier to handle. Various fabrication techniques have been proposed for polymeric belts including blow extrusion, spray coating, powder coating, electrodeposition, etc. A problem with polymeric belts is that they are not conducting. Some of the proposed solutions to this include loading the polymer with a conductive material such as carbon or coating a conductive layer of loaded polymer or other organic material. But these conductive materials are not as desirable as metals. One problem is that conductive (or conductively loaded) polymers have not been developed with proper blocking surfaces or layers required by photoreceptors. A thin metal coating could be applied to the polymer belt by vacuum deposition, but that process is expensive.
U.S. Pat. No. 4,686,016 discloses a method of electrodepositing a metal coating onto a surface of an endless belt. An annular bath is formed by a pair of endless belts and an aqueous electrolytic solution is filled into the annular bath. An anode is supported in the bath and one of the endless belts forms a cathode. The anode and cathode are connected to a constant voltage source and a metal coating is deposited on the belt acting as a cathode.
U.S. Pat. No. 4,758,486 discloses an endless belt shaped electrophotographic photoconductor comprising a support material and an electroconductive layer deposited thereon by vacuum evaporation. The electroconductive overcoating layer may comprise a polymeric material having a glass transition temperature of -10.degree. C. or lower.
U.S. Pat. No. 4,270,656 discloses a method of forming a rubber and fabric feed belt comprising the steps of 1) mounting a sleeve on a mandrel, 2) placing the mandrel in a mold, 3) pouring rubber into the mold, 4) removing the formed belt, 5) subjecting the belt to a halogenation treatment, and 6) grinding the outer surface of the belt.
U.S. Pats. Nos. 3,927,463, 3,950,839, and 4,067,782 disclose various methods of forming an electroforming mandrel used in the production of endless seamless nickel xerographic belts.
U.S. Pat. No. 4,747,992 discloses a process for forming at least one thin substantially uniform coating comprising applying polymeric film forming material on a cylindrical mandrel, solidifying the fluid coating to form a solid coating and separating the uniform solid coating from the mandrel.
U.S. Pat. No. 4,772,253 and Great Britain Patent No. 2,189,192 disclose a seamless belt comprising a layer of metal 10 to 50 micrometers thick and a lining layer made of flexible material such as synthetic resin or rubber provided on the inside surface thereof. The belt is used as a substrate for a photosensitive belt for an electrostatic photographic copying machine. The lining may be prepared by coating, bonding, adhesion or other methods.
There continues to be a need for improved, flexible, multilayered seamless belts for various applications including photoreceptor and ionographic substrates and a method of cost-effectively producing the same.